X-ray opaque marking means



Patented Feb. 15, 1949 X-RAY ()PAQUE MARKING MEANS No Drawing.Application July 27, 1944, Serial No. 546,907

12 Claims.

In the use of highly penetrating radiations such as alpha, beta or gammarays from radium or other radioactive substances, or where photographicplates or films are exposed, such as in metal inspections, medical andsurgical practice, etc., it has been customary to mark the plate or filmfor identification by placing formed letters of sheet lead for theidentifying data, such letters being laid on the casette or film holder,and by their shielding or blocking out the radiation, produce thedesired identification markings in the developed silver image. Suchprocedure, while positive in results, is inconvenient and particularlyawkward in many instances and not applicable to some purposes. Inaccordance with the present invention however, markings or blocking-outas desired may be applied on the film holder or casette or on a sheet ofmaterial laid thereon and can be easily and quickly removed therefromafter the exposure, the negative carrying the required markings orblocking, while the film holder is ready for re-use. Furthermore specialmarkings not available in stock forms may be employed and areas may becircled or otherwise identified or blocked out, as desired, all withimproved speed and facility. Other objects and advantages will appearfrom the following description.

To the accomplishment of the foregoing and related ends, the invention,then, comprises the features hereinafter fully described, andparticularly pointed out in the claims, the following descriptionsetting forth in detail certain illustrative embodiments of theinvention, these being indicative however, of but a few of the variousways in which the principle of the invention may be employed.

In accordance with the invent on, preferably a pencil or crayon isprovided comprising a material in fine particle size having metal atomsof high atomic weight, in a carrier or vehicle substance. By metal ofhigh atomic weight is here meant a metal of atomic weight at least 184.and particularly conveniently available are such metals as lead,bismuth, thallium, etc. Preferably, the metal is in colloidal form, asmay be provided by the known methods of preparing metals in colloidalcondition. With particular convenience, the carrier or vehicle may be awax, and if a water-soluble type of wax or material of wax consistencybe employed, after using the crayon or blocking-marking on the filmholder, such as a metal casette, it may be quickly removed by a dampcloth or like suitable means ready for the next use of the film holder.If

a non-water-soluble wax is used, the markings may be removed by use ofnaphtha or other vola tile wax solvent. Desirable water-soluble waxesare for instance the solid waxy polyglycols, polyethylene oxide(commercially known as Carboinstances of such suitable plasticizersbeing polyglycols, glycol ethers and esters, glycerine ethers andesters, etc.

As an example: A normally solid water-soluble wax, such as afore-noted,is melted, nad the heat is removed and as it begins to cool about 75 percent of colloidal lead having about '70 per cent or more of itsparticles in the size range of 1 to 15 microns, is stirred in, togetherwith 5 per cent of a polyglycol plasticizer to produce a rather thickpaste. The mixture is then formed into desired pencil or crayon shape,as by a mold or by extruding through a die, and allowed to cool andharden. The final product may be in the form of a stick or rod eithernot covered or covered with wood, metal, paper'or other casing adaptedto facilitate usage.

As another example: In similar procedure, the wax is melted and aboutper cent colloidal lead or other metal if high atomic weight in finelydivided form is incorporated in the wax together with about 15 per centof a uranium salt such as uranium sulphamate.

In similar manner, salts or compounds of the metals of high atomicweight, i.e. above 184, such as uranium, bismuth, thorium, lead,thallium, etc., may be applied along with the colloidal metal usually ofa lesser atomic weight and substituting a corresponding amount thereof.These combinations, including a heavier metal salt together with thefinely divided metal having a lesser atomic weight, possess improvedblocking power and are particularly useful for work in- VolVing gammarays and hard X-rays but are also fully effective for the softer lesspenetrating X-rays. Compositions omitting the heavier metal saltcomponent may be satisfactorily used wherever their blocking power issufficient, as for the softer, less penetrating X-rays.

In some instances instead of a normally solid 3 carrier, a liquid base,such as a cellulose ether or ester or an alkyd or Bakelite resin clearenamel or varnish dispersed in an organic solvent may have the desiredamount of colloidal metal or mixture of colloidal metal and compound ofheavy metal in proportions as aiore noted. Such composition mayzbe used.with amarking brush or pen.

With compositions as herein provided, identificartion markings such asin light metalalloy inspection work and other metal inspectionx'canwbequickly and conveniently made, and identification or blocking out manyextent-desired may be applied, and afterservingjitsipurp'osep may bequickly and easily removed," the finished photographic plate or filmcarrying. therdesired. Similarly in anatomical" marking or blocking.X-ray work, markings and blockings -may, be made as desired.

Other modes of applying the principle of the inventionmay be employed,change being made asnregards the details described; provided the' an'dthe like, comprising colloidal lead and acompoundv of a metal of atomic:Weight at least 184 and a normally soli'dwaxi' 3. A marking material forblocking x rays and the-dike; comprising colloidal. lead and'a compoundof a metal of atomic weight atleast 184-,- and a vehicle;

4. A marking material for blocking X-rays and 1 the like, comprising acolloidal. metal. of EtOmlCWElght-Elt least 184 and a normally solidwater-soluble material o-f'wax. consistency; 5. A marking" material. forblocking. X rays andthes like; OOmPTlSLiIIgT: a: colloidal. metal ofatomic" weight at least .1841-and a normally solid wax;

6:. A marking" material for blocking. X-rays and'.the-..like,zcomprising; a: colloidal metal of atomic weight=atleast 184; andavehicle;

'7. A marking material for blocking X-rays and the like, comprisingcolloidal lead, and a normally solid water-soluble material of waxconsistency.

8. A marking material for blocking X-rays and the like, comprisingcolloidal lead, and a normally. solid" Wax.

9; A marking material for blocking X-rays and the like, comprisingcolloidal lead, and a vehicle.

10. A vmarking material for blocking X-rays and the like, comprising avehicle with incorporated'coll-oidal metal of atomic weight at least184.

11. A marking .mat-erial for blocking X-rays and the-tlike,..comprisingcolloidal lead at least 50 per cent, polyglycol of wax consistency, anda small. percent of plasticizer.

12. A marking material for blocking X-rays and. the like, comprising acolloidal metal of atomic weight at least 184 in amount of at least 50per cent,'and a water-soluble polymerized ali-' phatie material of waxconsistency.

WILLIAM H. \VOOD.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 471,438 Schwarzwald Mar. 22, 18921,278,010 Poetschke Sept. 8, 1918 1,396,415 Fried Nov. 8, 1921 1,511,874Eder Oct. 14, 1924 1,602,688 Lindsay Oct. 12, 1936 1,918,996 Weger July18, 1933 2046,55? Holt July 7, 1936 2,162,178 Marasco June 13, 1939FOREIGN PATENTS Number Country Date 305,209 Great Britain 19 30 OTHER...REFERENCES Synthetic Organic;Chemicals, 10th.'Ed. 1940- published. by'Carbide and Carbon Chemicals Corp., N. Y. C. pp. 66-68. (Copy in-Div.64.)

